WO2022184404A1 - Circuit de décharge autonome pour décharger un condensateur - Google Patents

Circuit de décharge autonome pour décharger un condensateur Download PDF

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Publication number
WO2022184404A1
WO2022184404A1 PCT/EP2022/053317 EP2022053317W WO2022184404A1 WO 2022184404 A1 WO2022184404 A1 WO 2022184404A1 EP 2022053317 W EP2022053317 W EP 2022053317W WO 2022184404 A1 WO2022184404 A1 WO 2022184404A1
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WO
WIPO (PCT)
Prior art keywords
transistor
circuit
discharge
thermistor
discharge circuit
Prior art date
Application number
PCT/EP2022/053317
Other languages
German (de)
English (en)
Inventor
Berthold Fuld
Oliver Prior
Kevin Goebel
Original Assignee
Sma Solar Technology Ag
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sma Solar Technology Ag filed Critical Sma Solar Technology Ag
Publication of WO2022184404A1 publication Critical patent/WO2022184404A1/fr

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H02M1/322—Means for rapidly discharging a capacitor of the converter for protecting electrical components or for preventing electrical shock
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0006—Arrangements for supplying an adequate voltage to the control circuit of converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H02M1/327—Means for protecting converters other than automatic disconnection against abnormal temperatures

Definitions

  • the invention relates to a method for discharging a capacitance and a discharge circuit suitable for carrying out the method.
  • the invention also relates to an electrical device with such a discharge circuit.
  • the input capacitances are discharged, it is also ensured that DC supply lines connected to the input capacitance between the PV inverter and the PV generator are voltage-free, at least when an isolating device close to the generator is open. In this case, the input capacitances must also be safely discharged when the electrical device is switched off and/or is disconnected from its electrical supply during normal operation.
  • Document EP 2 248 238 B1 discloses a device for discharging a vehicle electrical system of an electric vehicle or an electrical component.
  • the device has a switchable resistor which is formed from a transistor and a PTC resistor which is connected to a source terminal of the transistor and thermally coupled to the transistor.
  • the control connection of the transistor is connected to a mains voltage.
  • the publication DE 102018006054 A1 discloses a device for discharging an electrical energy store via an actuating device and a Setting device comprehensive discharge path.
  • the temperature of the actuating device changes as a result of the discharge.
  • the actuating device is connected to a control device in a signal-conducting manner and can be brought into an electrically non-conductive open position and into an electrically conductive closed position as a function of a control signal from the control device.
  • the control signal is dependent on the temperature of the actuator.
  • Document WO 2019/158748 A1 discloses a discharge device for actively discharging an electrical network or an electrically operated unit, comprising a discharge circuit with a current-limiting resistor and a first switch for connecting a component to be discharged to a reference potential indirectly via the current-limiting resistor.
  • the discharge circuit also includes a limiting circuit arranged on the control terminal side of the first switch for limiting heating that occurs at the first switch and/or the current-limiting resistor during discharge operation.
  • the limiting circuit has an NTC resistor that is thermally coupled to the first switch and/or the current limiting resistor.
  • the disadvantage of these concepts is that a relatively high amount of energy is stored, particularly with a high electrical DC voltage in the range above 400 V, which DC voltage is common, for example, in PV generators and thus also in the input capacitances of PV inverters connected to them.
  • the discharge of this amount of energy in the specified time is associated with a correspondingly high electrical power during the discharge process, which in turn means a high thermal load on the transistor, and in the case of EP 2 248238 B1 also on the PTC resistor.
  • a discharge current would be reduced continuously through the transistor and the PTC resistor or the current-limiting resistor.
  • the voltage at the PTC resistor (EP 2248238 B1) or at the current-limiting resistor (WO 2019/158748 A1) counteracts a control voltage of the transistor, with the transistor being operated at least predominantly in its linear mode. This results in a high thermal load on the transistor.
  • PTC resistors are usually only for a small number thermal cycles and must be replaced after they have expired.
  • the cycle stability of the PTC resistor i.e. the number of permitted thermal cycles before the next component replacement, decreases as the thermal load within a cycle increases. However, reducing the discharge power to protect the transistor would result in the specified time for discharging the capacitance being exceeded.
  • the invention is based on the object of specifying an improved discharge circuit for a charged capacitance, with which the disadvantages mentioned above are avoided or at least significantly reduced.
  • temperature-sensitive components of the discharge circuit for example thermistors and semiconductor switches, should experience the lowest possible thermal load during a discharge process. In doing so, it must be ensured that the charged capacity is discharged within the specified period of time down to a DC voltage that is harmless when touched - usually ⁇ 60 V.
  • the discharge circuit should be designed to carry out the discharge of the capacitance even without an external energy supply and should also be able to be produced as cost-effectively as possible.
  • the object of the invention is to provide an electrical device in which the device's capacitances are discharged in a way that protects the components, particularly in a state in which the device is disconnected from its power supply.
  • the object of demonstrating an improved discharge circuit is achieved according to the invention with the features of independent patent claim 1 .
  • the object of demonstrating a method for discharging a capacitance is achieved according to the invention with the features of independent claim 13 .
  • the object of demonstrating an electrical device in which a device-internal capacitance is discharged in a way that protects the components even when the device is disconnected from a power supply is achieved according to the invention with the features of independent claim 16 .
  • Advantageous embodiments of the discharge unit are given in claims 2 to 12, advantageous embodiments of the method is in the Claim 14 and 15 mentioned.
  • An advantageous embodiment of the electrical device is described in claims 16 and 17.
  • a discharge circuit for discharging a capacitance comprises: an input with a first input connection and a second input connection for connection to a respective connection of the capacitance, a transistor whose drain connection is connected via a discharge resistor to the first input connection and whose source connection is connected to the second Input terminal is connected, a gate charging resistor connecting the first input terminal to a gate terminal of the transistor, a thermistor thermally coupled to the discharge resistor and / or the transistor.
  • the discharge circuit further comprises a switch with a conducting and a blocking switching state, which connects the gate terminal to the second input terminal, and is designed to change its switching state in response to a trigger signal, and a trigger circuit for controlling the switch, which is designed to generate the trigger signal for the switch depending on a temperature of the thermistor, and thus to control the switch depending on the temperature of the thermistor.
  • the discharge circuit is characterized in that it is set up to be supplied from a voltage present at the input terminals, and that the switch and/or a combination of the trigger circuit and the switch is set up to determine the switching state of the switch in response to the trigger signal, and thus also depending on the temperature of the thermistor, to change abruptly from the blocking to the conducting switching state in order to generate a transient change from a first operating state BZ1 of the discharge circuit when the transistor is switched on to a second operating state BZ2 of the discharge circuit when the transistor is switched off.
  • the transistor can be in the form of a field-controlled transistor.
  • this can be a field effect transistor (FET).
  • FET field effect transistor
  • IGBT insulated gate bipolar Transistor
  • the description is given throughout with terminal designations related to an FET.
  • the following assignments apply to the terminal designations of the transistor: the source terminal of the FET corresponds to an emitter terminal of the IGBT , the drain terminal of the FET corresponds to a collector terminal of the IGBT .
  • the gate - Connection usually retains its designation.
  • the capacitance is discharged via the discharge circuit according to the invention.
  • the discharge circuit has a first operating state BZ1 with the switch open and the transistor turned on, and a second operating state BZ2 with the switch closed and the transistor blocked.
  • the procedure includes the following steps:
  • the discharge circuit Operating the discharge circuit as a function of a temperature of the thermistor in one of the first BZ1 and the second operating state BZ2, the discharge circuit being operated in a stationary manner in the first operating state BZ1 when the temperature of the thermistor is below a temperature threshold value TTH, and the discharge circuit is operated with a repetitive change between the first operating state BZ1 and the second operating state BZ2 when the temperature of the thermistor is greater than or equal to the temperature threshold value TTH, so that the transistor changes between the on and off state in a repeated manner
  • the discharge circuit according to the invention is designed and set up to be operated in accordance with the method according to the invention when a capacitance is connected to its input.
  • the invention makes use of the effect that linear operation of the transistor is prevented when the capacitance is discharged, but is at least reduced to the greatest possible extent. Rather, the transistor—and thus the discharge circuit—operates primarily in two operating states, the first operating state when the transistor is on and the second operating state when the transistor is off. A change from the first to the second operating state is initiated by the switch, by the switch itself, or by the switch in conjunction with the trigger circuit suddenly changes its switching state from the blocking to the conducting state. Since the gate terminal of the transistor is connected to the second input terminal when the switch is in the on state, a transient change occurs in response thereto from the first operating state BZ1 of the discharge circuit when the transistor is turned on to the second operating state BZ2 of the discharge circuit when the transistor is off.
  • the discharge resistor is dimensioned such that in the first operating state BZ1, a large part of the power loss when the capacitance is discharged is converted in the discharge resistor and not in the transistor.
  • the second operating state BZ2 a discharge of the capacitance is temporarily not only reduced by the blocking transistor, but suppressed. Even when the transistor is off--and quasi-temporarily suppressed discharge of the capacitance--a power loss converted at the transistor is significantly reduced in comparison to a more permanent operation of the transistor in its linear range. The reason for this is that in the present case the power loss of the transistor is reduced to a considerable extent to its switching losses.
  • the discharge circuit according to the invention is then operated in the first operating state BZ1 with the transistor switched on when a temperature of the thermistor thermally coupled to the transistor and/or the discharge resistor falls below the temperature threshold value TTH.
  • TTH temperature threshold value
  • the discharge of the capacitance is not only reduced but at least temporarily suppressed by the discharge circuit being switched to the second operating state BZ2 with the transistor off by suddenly closing the switch.
  • the discharge circuit is at least briefly in a repeated manner via the gate charging resistor with the switch at least temporarily open into the first Operating state BZ1 added to then, when the temperature of the thermistor in the first operating state BZ1 still reaches the temperature threshold value TTH or exceeds it, to switch back to the second operating state BZ2 when the transistor is off by abruptly closing the switch.
  • a transient change that repeats over time, in particular several times, takes place between the first operating state BZ1 with the transistor turned on and the second operating state BZ2 with the transistor turned off.
  • the duration of the second operating state BZ2 is usually significantly longer than the duration of the first operating state, which is why the capacitance discharges comparatively little over time at temperatures of the thermistor above the temperature threshold value. Only when the temperature of the thermistor has reduced again to such an extent that it is below the temperature threshold value TTH is the first operating state BZ1 maintained for a longer period of time, at least maintained until the thermistor also permanently (er ) flowing discharge current has heated up again to a temperature which corresponds to the temperature threshold value TTH or exceeds it.
  • both the method according to the invention and the discharge device according to the invention result in a permanent, uninterrupted discharge of the capacitance at temperatures of the thermistor below the temperature threshold value TTH.
  • the discharge of the capacitance is predominantly suppressed over time, but is repeatedly interrupted by comparatively short discharge pulses.
  • Most of the power loss in the discharge path is converted to the discharge resistor, but not to the transistor. Since the discharge resistor is arranged between the drain connection of the transistor and the first input connection of the discharge circuit, the transistor is not operated in its linear operating range, at least only for as short a time as possible.
  • the discharge circuit can therefore also with discharges of high DC voltages present between the input terminals.
  • the discharge circuit can be used, for example, with DC voltages above 400 V, advantageously above 1000 V, particularly preferably even above 1400 V.
  • the discharge circuit and the method for its operation is suitable for ensuring sufficiently rapid discharge of the capacitance even with such high DC voltages, without subjecting the transistor to a high load, as would otherwise occur in the case of predominantly linear operation of the transistor.
  • Such DC voltages are, for example, quite common at a DC input of a PV inverter, which is why the discharge circuits can also be used particularly advantageously in a PV inverter.
  • the discharge circuit is electrically powered from the charged capacitance. It is therefore designed to operate properly in an electrical device even when the electrical device is disconnected from its normal electrical supply. Even if the capacitance cannot be discharged, for example because it is recharged from a DC source that is incorrectly still connected to the capacitance, the discharge circuit or its components are protected from damage or destruction as a result of the fault.
  • the method according to the invention can operate with only one temperature threshold value TTH of the thermistor. In this case, there is an entry “into” the steady-state operation of the discharge circuit in the first operating state BZ1, as well as an exit “from” the steady-state operation of the discharge circuit in the first operating state BZ1 at the same temperature threshold value TTH. In an advantageous embodiment of the method, however, the "exit from” the stationary operation of the discharge circuit in the first operating state BZ1 at the temperature threshold TTH and the "entry into” the stationary operation of the discharge circuit in the first operating state BZ1 at a second temperature threshold TTH , 2 take place.
  • a stable and robust overall operation of the discharge circuit can be supported via the second temperature threshold value TTH.2 and a flysteresis behavior associated therewith.
  • operation of the discharge circuit at a temperature of the thermistor between the temperature threshold value TTH and the second temperature threshold value TTH.2 can depend on a temperature of the thermistor that prevailed shortly beforehand. For example, operation may depend on whether the thermistor is actually cooling or heating.
  • the operation of the discharge circuit can last as a function of the temperature of the thermistor until a DC voltage falling across the capacitance and therefore present at the input terminals of the discharge circuit falls below a voltage threshold value UTH.
  • the voltage threshold may correspond to a DC voltage close to 0V. However, it can also be sufficient if the capacitance has only discharged to a DC voltage that does not pose a risk if touched.
  • the voltage threshold value UTH can be e.g. 12 V, 30 V, possibly also 60 V, depending on the relevant standards.
  • the switch of the discharge circuit can be designed as a bistable switch and can include a thyristor, for example.
  • a bistable switch within the meaning of the application is in particular a switch that is free of a linear working range. It therefore includes a conducting and a blocking switching state, but no transition region between the conducting and the blocking switching state in which an ohmic resistance in a power path of the switch changes continuously or steadily.
  • the switch can also have a linear operating range and, for example, comprise a transistor, in particular a MOSFET transistor or an IGBT transistor.
  • the trigger circuit can then be designed as a flip-flop, which ensures that the switch occurs in a sudden manner when its switching state changes, in particular when changing from the blocking to the conducting switching state, i.e. that the linear transition range that may be present quickly is run through.
  • the switch can change his blocking to its conductive switching state within 10 ps, advantageously within 5 ps, particularly preferably change within 1 ps.
  • the discharge circuit can additionally have a voltage stabilization unit, which contains, for example, a zener diode or a parallel circuit made up of a zener diode and a buffer capacitor.
  • a voltage stabilization unit which contains, for example, a zener diode or a parallel circuit made up of a zener diode and a buffer capacitor.
  • the cathode of the zener diode is connected to the gate connection of the transistor and the anode of the zener diode is connected to the second input connection.
  • the voltage stabilization unit is designed to charge its buffer capacitor by a current emanating from the first input connection via the gate charging resistor up to a value of a DC voltage predetermined by the zener diode.
  • the buffer capacitor and the gate charging resistor are dimensioned in such a way that the buffer capacitor can be charged to the value specified by the zener diode within a minimum of 0.2 s and a maximum of 4 s, particularly preferably a minimum of 0.5 s and a maximum of 2 s is completed.
  • the gate charging resistor can advantageously be dimensioned in such a way that a current limited by it and emanating from the first input terminal is less than a holding current of the thyristor is. This ensures that the switch designed as a thyristor, when it is in its conducting switching state, can be switched back to the blocking switching state due to the current flowing through it, which is limited by the gate charging resistor.
  • the thermistor may be formed as a component of the trigger circuit, in other words the trigger circuit may include the thermistor.
  • the thermistor can include a PTC thermistor (also called a PTC resistor).
  • PTC thermistor also called a PTC resistor
  • it can advantageously also be in the form of a thermistor (also called an NTC resistor).
  • a thermistor usually has a higher cycle stability than a PTC thermistor, so it can go through several load cycles within each of the load cycles under the same thermal load before it should be replaced for safety reasons.
  • the thermistor possibly also the other components or all components of the trigger circuit can be arranged in the discharge path, the Series connection of discharge resistor and transistor is formed.
  • the thermistor Since the thermistor is arranged in the discharge path, at least part of the discharge current flows through it itself. It therefore heats up not only because of its thermal coupling to the discharge resistor and/or the transistor, but also as a result of the discharge current itself. This can be advantageous with regard to a rapid response from the trigger circuit.
  • the discharge resistor arranged in the discharge path can be designed as a single discharge resistor.
  • the discharge resistor can include a multiplicity of resistors connected in series and/or in parallel with one another. In the latter case, the power to be converted is distributed over several resistors.
  • the thermistor can be thermally coupled to only one resistor--preferably a resistor arranged centrally within the plurality of resistors--or to a plurality of resistors.
  • the trigger circuit can be implemented in different ways. Four advantageous options for implementing the trigger circuit are shown and explained in detail in FIGS. 3a-3c and 4 as examples, which is why reference is made here to the corresponding figures and descriptions of the figures.
  • An electrical device comprises a capacitance and a discharge circuit according to the invention acting on the capacitance.
  • the electrical device is designed and set up, in particular its discharge circuit, for carrying out the method according to the invention.
  • the electrical device is set up by means of the discharge circuit to also discharge the device-internal capacitance in a state in which the device is disconnected from its energy supply.
  • the electrical device can in particular be a photovoltaic (PV) inverter.
  • the PV inverter can be designed as a PV inverter with only one DC input for connecting a PV string or as a so-called multi-string PV inverter with multiple DC inputs each having an input capacitance for connecting multiple PV strings.
  • the capacitance can therefore include one or more input capacitances of the PV inverter that are decoupled by diodes.
  • the electrical device can therefore advantageously have a switching unit that acts on the gate connection of the transistor and can be controlled by a controller of the device, which is set up to suppress or enable a discharge of the capacitance depending on a control signal from the device-internal controller.
  • the switching unit can contain, for example, a further switch arranged between the gate connection and the source connection of the transistor, which, in response to a control signal from the device-internal controller, connects the gate connection of the transistor to the source connection of the transistor with low resistance and thus Transistor of the discharge device permanently blocks, whereby a discharge of the capacity during operation of the device is deliberately suppressed.
  • FIG. 1 shows an embodiment of a discharge circuit according to the invention in one embodiment
  • FIG. 2 shows an embodiment of a method according to the invention in the form of a flow chart
  • FIG. 3a shows a trigger circuit for driving a switch, designed as a thyristor, in the discharge circuit in a first embodiment.
  • 3b shows a trigger circuit for driving a switch, designed as a thyristor, of the discharge circuit in a second embodiment.
  • 3c shows a trigger circuit for driving a switch, designed as a thyristor, in the discharge circuit in a third embodiment.
  • 4 shows a trigger circuit in a fourth embodiment for driving a switch, designed as a transistor, of the discharge circuit.
  • the discharge circuit 100 has an input 101 with a first input connection 101a and a second input connection 101b, to which a capacitance 1 to be discharged is connected.
  • a discharge path 10 is connected in parallel with the input 101 and the capacitance 1 and is formed as a transistor 3 from a series connection of a discharge resistor 2 and a field-controlled transistor (FET, here: exemplarily as a MOSFET).
  • the FET 3 has its drain terminal 3D connected via the discharge resistor 2 to the first input terminal 101a.
  • a source connection 3S of the FET 3 is connected to the second input connection 101b, which in turn is connected to a reference potential GND.
  • the discharge circuit 100 has a series circuit made up of a gate charging resistor 9 and a voltage stabilization unit 7, which is formed by a parallel circuit made up of a zener diode ZD1 and a buffer capacitor C1.
  • the gate charging resistor 9 is connected to the first input connection 101a and the anode of the zener diode ZD1 is connected to the second input connection 101b.
  • a switch 6 is arranged in parallel with the zener diode ZD1.
  • the switch 6 is controlled via a trigger circuit 5, which is symbolized by an arrow illustrated in dashed lines pointing towards the switch 6.
  • the switch 6 is controlled by the trigger circuit 5 as a function of a temperature of a thermistor 4, which is symbolized in FIG. 1 by an arrow pointing towards the trigger circuit 5.
  • the trigger circuit 5 can be set up to drive the switch 6 as a function of a DC voltage UGS between the gate connection 3G and the source connection 3S of the transistor 3 .
  • the thermistor 4, which is shown as an example in Figure 1 as a thermistor (NTC), is thermally connected to the discharge resistor 2 and/or to the FET 3 coupled. The thermal coupling of the thermistor 4 is symbolized by double arrows in FIG.
  • the thermistor 4 and the trigger circuit 5 are each shown as separate components in FIG. 1, the thermistor 4 may be an integral part of the trigger circuit 5.
  • the discharge circuit 100 it is possible for the discharge circuit 100, but not absolutely necessary, to arrange the thermistor 4 and at least parts of the trigger circuit 5, possibly also the entire trigger circuit 5, in the discharge path 10. Two possible variants of such a connection within the discharge path 10 are symbolized in FIG. Reference is made to the circuit positions 13, 14 and their connection points in connection with the different embodiments of the trigger circuits 5 illustrated in FIGS. 3a-3c and 4.
  • FIG. 2 shows an embodiment of the method according to the invention in the form of a flow chart, as can be carried out with a discharge circuit according to FIG. 1 installed in a device, for example a PV inverter.
  • the method starts with a method step S1.
  • the electrical device comprising the discharge circuit is initially operated in its normal mode in a method step S2.
  • the discharge circuit 100 is disabled.
  • the device is switched off, the discharge circuit 100 being activated automatically.
  • a fourth method step S4 it is checked whether an input voltage Uein present at the input 101 of the discharge circuit 100 falls below a voltage threshold value UTH. If this is not the case, then the capacitance 1 connected to the input 101 is not yet sufficiently discharged and the method branches to a fifth method step S5. In the fifth method step S5, it is checked whether a temperature T of the thermistor 4 is lower than a temperature threshold value TTH.
  • the process branches to a sixth method step S6, in which the discharge circuit 100 is operated in the first operating state BZ1 with the transistor 3 switched on. Capacitance 1 is discharged by an uninterrupted flow of current.
  • the method branches from the sixth method step S6 back to the fourth method step S4. If, on the other hand, the temperature T of the thermistor 4 is greater than or equal to the temperature threshold value TTH, SO during the check in the fifth method step S5, the method branches to a seventh method step S7, in which the discharge circuit 100 alternates between the second operating state BZ2 with the transistor 3 blocking and the first operating state BZ1 changes back and forth when transistor 3 is switched on.
  • the first operating state BZ1 is usually assumed to be significantly shorter than the second operating state BZ2.
  • the capacity 1 is discharged by a cyclically interrupted discontinuous flow of current.
  • the time periods in which the first operating state BZ1 is assumed are usually significantly shorter than the time periods in which the second operating state BZ2 is present, there is no significant discharge of the capacitance 1 in the seventh method step S7.
  • the method branches back to the fourth method step S4. If it is now determined in the fourth method step S4 that the DC voltage Uin present at the input 101 is less than the voltage threshold value UTH, then the capacitance 1 connected to the discharge circuit 100 is sufficiently discharged and the method is repeated in an eighth method step S8 completed.
  • a loop of method steps S4-S7 is shown in separate blocks in the flow chart in order to explain the function of the method. According to the method, however, it is possible, and in the case of a discharge circuit that operates largely analogously, it is also common for the method steps S4-S7 to be run through almost simultaneously within the loop.
  • FIG. 3a shows a first embodiment of a trigger circuit 5, such as can be used within the discharge circuit 100 in FIG. 1, for example.
  • the switch 6 of the discharge circuit 100 is designed as a thyristor 11 here.
  • the trigger circuit 5 has a parallel circuit made up of the PTC thermistor 21 and a series circuit made up of a second Zener diode ZD2 and a second resistor R2. In this case, a connection point 28 between the second Zener diode and ZD2 connected to the second resistor R2 to a control terminal 11 G of the switch 6 designed as a thyristor 11 .
  • the trigger circuit 5 can be arranged at the second circuit position 14 within the discharge path 10 of the discharge circuit 100 between the source connection 3S of the transistor 3 and the reference potential GND or the reference potential GND. This is symbolized by the connection points 14a, 14b also shown in FIG. 3a
  • connection points within FIG. 1 correspond.
  • an arrow is directed from the connection points 14a, 14b to the source connection 3G or the reference potential GND, which again characterizes the arrangement of the trigger circuit 5 within the discharge circuit 100.
  • the current flowing in the discharge path 10 flows through the PTC thermistor 21 as a thermistor 4 during the first operating state BZ1. It therefore heats up both as a result of the thermal coupling with the discharge resistor 2 and/or the transistor 3 and as a result of the current passing through it.
  • the heating of the PTC thermistor 21 increases its ohmic resistance and thus the voltage drop between the connection points 14a, 14b. If the voltage drop exceeds a threshold value defined by the second zener diode ZD2, then the thyristor 11 receives a voltage signal at its control terminal 11G and is fired, as a result of which it suddenly becomes conductive.
  • the control terminal 3G of the transistor 3 is connected to its source terminal 3S, as a result of which the buffer capacitor C1 of the voltage stabilization unit 7 is discharged and the transistor 3 is switched to its blocking state.
  • the current limited by the gate charging resistor 9 flows from the first input terminal 101a through the thyristor 11. However, this is less than a holding current of the thyristor, as a result of which the thyristor 11 is switched back to its blocking state.
  • the current limited by the gate charging resistor 9 now begins to charge the buffer capacitor C1 to the value set by the zener diode ZD1.
  • the voltage at the gate terminal 3G of the transistor 3 increases accordingly and the transistor 3 is turned on again.
  • the thyristor 11 is fired again immediately and switched to its conductive switching state. This alternating change is repeated until the temperature of the thermistor 4 exceeds the temperature threshold falls below TTH, as a result of which the transistor 3 again remains permanently turned on. If the capacity 1 is sufficiently discharged, the discharge circuit 100 is no longer supplied and the method ends automatically.
  • FIG. 3b shows a second embodiment of the trigger circuit 5, which can also be arranged in the second circuit position 14 within the discharge path. It is similar in structure and functional behavior to the first embodiment shown in FIG. 3a. The differences from the first embodiment are therefore mainly presented below.
  • the second embodiment of the trigger circuit 5 has a parallel connection made up of a third zener diode ZD3 and a series connection made up of a flow-through conductor 22 and a third resistor R3.
  • a connection point 29 is connected between the floating conductor 22 and the third resistor R3 and to a control connection 11G of the switch 6 designed as a thyristor 11 .
  • the voltage drop between the connection points 14a, 14b is specified by the third zener diode ZD3.
  • the flow conductor 22 heats up, its ohmic resistance decreases and a voltage present at the connection point 29 increases relative to the reference potential GND.
  • a voltage threshold value required for the thyristor 11 is reached, the thyristor 11 is fired and switched to its conductive state.
  • the further functional behavior including the alternating change between the conducting and the blocking switching state of the thyristor 11, corresponds to the behavior already described in FIG 22, and not caused by an increase in the ohmic resistance of the PTC thermistor, as in FIG. 3a. Therefore, reference is made to the explanations in the description of FIG. 3a for the basic functional behavior.
  • FIG. 3c A third embodiment of the trigger circuit 5 is illustrated in FIG. 3c.
  • the third embodiment of the trigger circuit 5 includes an optocoupler 23.
  • the trigger circuit 5 is not complete here, but only partially in the discharge path 10 arranged. Specifically, a first part shown on the left in Fig. 3c is arranged at the first circuit position 13 between the transistor 3 and the discharge resistor 2, which in turn is symbolized by correspondingly drawn connection points 13a 13b, which also correspond to the connection points 13a, 13b within Fig. 1 .
  • the first part of the trigger circuit 5 has a structure similar to the second embodiment of the trigger circuit shown in FIG.
  • a series circuit comprising a fifth Zener diode ZD5 and a diode of the optocoupler 23 is arranged in parallel with the fourth resistor R4.
  • a further part of the trigger circuit 5 includes a series circuit made up of a fifth resistor R5, a transistor associated with the optocoupler 23 and a sixth resistor R6.
  • the series circuit is connected at one end (here first connection point 15a) to the first input connection 101a and at the other end (here: further connection point 15b) to the reference potential GND.
  • the part of the trigger circuit 5 shown on the left operates similarly to the second embodiment according to FIG. 3b.
  • a voltage present at the connection point 30 increases relative to a voltage present at the connection point 13b. If the voltage at the connection point 30 exceeds a threshold value specified by the fifth zener diode ZD5, this results in a current flow through the diode of the optocoupler 23, as a result of which the—previously blocked—transistor of the optocoupler 23 is turned on.
  • a DC voltage present at the further connection point 31 is raised relative to the reference potential present at the further connection point 15b, as a result of which the switch 6 designed as a thyristor 11 is fired and switched to its conducting switching state.
  • FIG. 3a shows a fourth specific embodiment of the trigger circuit 5 which, in contrast to the previously described specific embodiments, is not arranged in the discharge path 10 of the discharge circuit 100 .
  • it is connected to a first connection point 16a with the gate connection 3G of the transistor 3, which is symbolized in FIG. 4 by an arrow emanating from the connection point 16a and directed towards 3G.
  • a second connection point 16b of the trigger circuit 5 is connected to the reference potential GND of the discharge circuit, which is symbolized in FIG. 4 by an arrow emanating from the second connection point 16b and pointing towards GND.
  • the fourth embodiment of the trigger circuit 5 is designed as a flip-flop and acts to control a transistor 12 as a switch 6.
  • the trigger circuit 5 contains a so-called Schmitt trigger circuit 32.
  • the Schmitt trigger circuit 32 has a resistance bridge made of a thermistor 22 as a thermistor 4, a seventh R7, an eighth R8 and a ninth resistor R9.
  • a connection point of a series connection made up of the seventh resistor R7 and the thermistor 22 is connected to a positive input of an operational amplifier 35, and a connection point of a series connection made up of the eighth resistor R8 and the ninth resistor R9 is connected to a negative input of the operational amplifier 35.
  • An output of the operational amplifier 35 is connected to the connection point of the seventh resistor R7 and the thermistor 22 via a tenth resistor R10 in the form of positive feedback.
  • the Schmitt trigger circuit 32 is supplied from a voltage stabilization circuit 33 comprising a parallel connection of a sixth zener diode ZD6 and a second buffer capacitor C2.
  • the voltage stabilization circuit 32 is fed from a voltage present at the gate connection 3G of the transistor 3, namely via a series circuit made up of an eleventh resistor R11 and a second diode D2, which is connected to the first connection point 16a of the trigger circuit 5.
  • the output of the operational amplifier 35 is connected to a gate connection 12G of the switch 6, which is designed as a further transistor 12, specifically as a further FET 12, in FIG.
  • the further transistor 12 can also be in the form of a bipolar transistor, optionally also present together with the operational amplifier 35 in an integrated circuit (IC).
  • a hysteresis behavior in relation to a change in the switching states of the further transistor 12 as a function of the temperature of the thermistor 4 is generated by the Schmitt trigger circuit.
  • the further transistor 12 is in a blocking switching state when the temperature T of the thermistor 4 is low.
  • the discharge circuit 100 is operated in the first operating state BZ1 with the transistor 3 switched on. As the temperature of the discharge resistor 2 and/or the transistor 3 increases, the thermistor 4 is heated and the resistance of the thermistor 22 decreases.
  • the temperature threshold value TTH When the temperature threshold value TTH is reached or exceeded, there is a sudden change in the output voltage of the operational amplifier 35 from a “low signal” to a “high signal”, as a result of which the further transistor 12 is switched on. As a result, the gate terminal 3G of the transistor 3 is connected to the reference potential GND and the discharge circuit 100 is switched to the second operating state BZ2 when the transistor 3 is off.
  • the thermistor 4 cools down, on the other hand, the resistance of the NTC thermistor 22 decreases.
  • the second temperature threshold value TTH .2 is smaller than the temperature threshold value TTH , that is to say TTH .2 ⁇ TTH applies. Such a hysteresis behavior is usually advantageous with regard to a robust and stable overall operation of the discharge circuit 100 .
  • the operational amplifier 35 is deactivated when the DC voltage falls below a minimum level and the further transistor 12 as switch 6 is switched back to its blocking switching state.
  • this switching state of the switch 6 is only present for a short time if the temperature T of the thermistor 4 does not correspond to permanent operation of the discharge circuit 100 in the first operating state BZ1. Rather, when the switch 6 is briefly off, the gate connection 3G is recharged via the gate charging resistor 9, and thus also the voltage stabilization unit 33, and the switch 6 is switched back to its conducting switching state.
  • the above-mentioned alternating change between the second operating state BZ2, which is predominantly present in terms of time, and the first operating state BZ1, which is present for a short time, of the discharge circuit 100 also occurs in the fourth specific embodiment of the trigger circuit 5.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Power Conversion In General (AREA)

Abstract

L'invention concerne un circuit de décharge (100) pour décharger un condensateur (1), qui comprend une entrée (101) pour la connexion électrique du condensateur (1) ; un transistor (3) dont la borne de drain (3D) est connectée au moyen d'une résistance de décharge (2) à une première borne d'entrée (101a) et dont la borne de source (3S) est connectée à la deuxième borne d'entrée (101b) ; une résistance de charge de grille (9) qui relie la première borne d'entrée (101a) à une borne de grille (3G) du transistor (3) ; une thermistance (4) qui est reliée thermiquement à la résistance de décharge (2) et/ou au transistor (3) ; et un commutateur (6) qui relie la borne de grille (3G) à la deuxième borne d'entrée (101b) ; et un circuit de déclenchement (5) qui est conçu pour commander le commutateur (6) en fonction d'une température de la thermistance (4). Le circuit de décharge (100) est conçu pour être alimenté à partir d'une tension d'alimentation appliquée aux bornes d'entrée (101a, 101b) ; le commutateur (6) et/ou une combinaison du circuit de déclenchement (5) et du commutateur (6) permettant de changer l'état de commutation du commutateur (6) de façon abrupte de l'état de blocage à l'état conducteur, afin que soit généré un changement transitoire d'un premier état de fonctionnement (BZ1) du circuit de décharge (100) lorsque le transistor (3) est sous tension à un deuxième état de fonctionnement (BZ2) du circuit de décharge (100) lorsque le transistor (3) est hors tension. L'invention concerne en outre un procédé de décharge d'un condensateur et un appareil électrique équipé d'un tel circuit de décharge.
PCT/EP2022/053317 2021-03-02 2022-02-11 Circuit de décharge autonome pour décharger un condensateur WO2022184404A1 (fr)

Applications Claiming Priority (2)

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DE102021105023.5 2021-03-02
DE102021105023.5A DE102021105023B4 (de) 2021-03-02 2021-03-02 Entladeschaltung zum Entladen einer Kapazität, Verfahren zur Entladung einer Kapazität über die Entladeschaltung und elektrisches Gerät mit einer derartigen Entladeschaltung

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110241581A1 (en) * 2008-12-11 2011-10-06 Stefan Flock Vehicle having a power supply device for an electric motor and method for supplying power to the electric motor
EP2248238B1 (fr) 2008-02-25 2015-07-22 Robert Bosch GmbH Circuit de decharge pour reseaux de tension elevee
WO2019158748A1 (fr) 2018-02-19 2019-08-22 Brose Fahrzeugteile GmbH & Co. Kommanditgesellschaft, Würzburg Dispositif de décharge, unité électrique et procédé de décharge
DE102018006054A1 (de) 2018-08-01 2020-02-06 A.B. Mikroelektronik Gesellschaft Mit Beschränkter Haftung Vorrichtung zum zumindest teilweisen Entladen eines elektrischen Energiespeichers
CN111697809A (zh) * 2020-07-20 2020-09-22 阳光电源股份有限公司 一种开关电源及其控制方法
EP3745577A1 (fr) * 2019-05-28 2020-12-02 Fronius International GmbH Source de courant d'inverseur

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2248238B1 (fr) 2008-02-25 2015-07-22 Robert Bosch GmbH Circuit de decharge pour reseaux de tension elevee
US20110241581A1 (en) * 2008-12-11 2011-10-06 Stefan Flock Vehicle having a power supply device for an electric motor and method for supplying power to the electric motor
WO2019158748A1 (fr) 2018-02-19 2019-08-22 Brose Fahrzeugteile GmbH & Co. Kommanditgesellschaft, Würzburg Dispositif de décharge, unité électrique et procédé de décharge
US20210008983A1 (en) * 2018-02-19 2021-01-14 Brose Fahrzeugteile SE & Co. Kommanditgesellschaft, Würzburg Discharging device, electrical unit and discharging method
DE102018006054A1 (de) 2018-08-01 2020-02-06 A.B. Mikroelektronik Gesellschaft Mit Beschränkter Haftung Vorrichtung zum zumindest teilweisen Entladen eines elektrischen Energiespeichers
EP3745577A1 (fr) * 2019-05-28 2020-12-02 Fronius International GmbH Source de courant d'inverseur
CN111697809A (zh) * 2020-07-20 2020-09-22 阳光电源股份有限公司 一种开关电源及其控制方法

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